Slow or improper wound healing compromises the quality of life for large numbers of people. One particular type of wound healing where problems can occur is the healing of tympanic membrane (eardrum) perforations. Although the majority of perforations will heal spontaneously, and are closed by proliferating keratinizing squamous epithelium advancing ahead of an ingrowing connective tissue, some perforations do not heal, frequently resulting in loss of hearing or other complications. It is still an open question why some perforations heal, whereas others stay patent. In addition, every year in the United States more than 1.25 million people suffer from burns, and 6.5 million have chronic skin ulcers caused by pressure, venous stasis, or diabetes mellitus.
Wound healing is a dynamic tissue remodeling process involving the formation of a matrix rich in fibrin and fibronectin in the wound field, infiltration of neutrophils and macrophages, proliferation of epidermal keratinocytes at the wound edges and their migration through the provisional matrix, formation of granulation tissue containing newly developed vessels and migrating inflammatory cells and fibroblasts, and wound contraction. Wound healing studies of skin suggest that proteases play important roles in several steps. It is well documented that the degradation of the extracellular matrix (ECM) that takes place during wound healing and other ECM remodeling processes is dependent on the action of a variety of proteolytic enzymes secreted by inflammatory cells, as well as by stromal tissue cellular elements. Many different proteinases are thought to contribute to matrix remodeling during wound healing (Saksela and Rifkin, Annu. Rev. Cell Biol. 4, 93-126 (1988)). However, the precise mechanisms responsible for this process, and how they are regulated, are poorly understood.